Temperature compensation means for pressure actuated indicators



April 18, 194.4, A. E. slDwELl. 2,347,134

. TEMPERATURE COMPENSATION MEANS FOR PRESSURE ACTUATED INDICATORS u Filed June 29, 1938 2 sheets-sheet 1 fla-1 -Pl'il 18,1944a A. E. SIDWELL 2,347,134

TEMPERATURE COMPENSATION MEANS FOR PIRESSURE-ACTUATED INDICATORS Filed June 29, 1938 2 Sheets-Sheet 2 /5/ INVENTR.

ATTORNEY.

` perature.

Patented Apr. 18, 1944- TEMPERATURE COMPENSATION MEANS FOR PRESSURE ACTUATED INDICATORS Alfred E. Sidwell, Kew Gardens, N. Y.,

Bendix Aviation Corporation,

assignor to South Bend, Ind.,

a corporation of Delaware Application June 29, 1938, Serial No. 216,580 (cl. 'z3- 179) 12 Claims.

The present invention relates to pressure responsive indicating instruments and more particularly to instruments of the type wherein a differential between the pressures on two sides of a pressure responsive element, established by a `changevin one of said pressures, is utilized to operate an indicator, and wherein means are provided for the equalization of saidA pressu'es, when said change no longer takes place. An example of such an instrument is a rate-of-climb indicator andthe invention is illustrated and described hereinafter in connection with such 'an instrument, but it will be understood that it is not restricted to this particular use and may -be embodied in aneroid; altimeters, manifold pressure gauges, airspeed indicators and the like.

Similar devices of the prior art have been utilized wherein, due to changes in temperature, changes in the pressure differential have been produced which were not trulyvindicative of the value of the quantity varying with said changes. In such devices of the prior art. it has been the practice to provide means controlled by-changes in temperature to control, eliminate or offset the 'A changes in pressure due to said changes in temperature.

Even with the utilization of such temperature responsive devices for compensating for changes in temperature, the devices were either completely or partly inapplicable to the solution of the didiculty, upon sudden changes in temperature, and the temperature compensation achieved has not been commensurate with the amount of error introduced by the temperature change.

In view of the above conditions prevailing inl the prior art, one of the objects ofthe present invention is to provide novel temperature compensating means whereby the foregoing undesirable characteristics are eliminated.

Another object of the invention is t'o provide novel compensating means wherein the compensating eect is produced by a rate of change cf temperature in contra-distinction to compensationvproduced by thc amount of change of tem- A further object is to provide a novel method of temperature compensation whereby errors due ments-of the instrument, are utilized to provide temperature compensation,

Still another object is to provide novel .com-

pensating means for compensating for the rate of change of temperature in an indicating instrument of the pressure responsive type.

A further object is to provide a novel instrument of the class described which requires substantially no insulation against changes in temperature.

Still another object is to provide a novel rate of climb indicator of dependable performance which will be accurate under all changes and rates of change in temperature.

The above and further objects and advantages of the invention will appear more fully hereinafter l from a consideration of the detailed description which follows, taken together with the accomto sudden changes lin temperature are ccmpsnsated lby utilization of a force proportional to the rate of change of temperature.

Still another object is to provide a novel instrument of the type characterized above in which means expanding and contracting with changes in temperature, at a rate different from the rate of expansion or contraction ofthe remaining ele;

panying drawings wherein are illustrated several embodiments of the invention. It is to be expressly understood, however, that the drawings are for purposes of illustration and description only and are not designed as a deinition of the limits of the invention, reference primarily being had for this purpose to the appended claims.

In the drawings, wherein like reference char.

acters refer to like parts throughout the several views:

Fig. l is a side elevation, in-section, of the operating mechanism and casing of one embodi-` ment of the present invention;

Fig. 2 is an enlarged sectional view of the compensating means shown in Fig. 1, illustrating the means for attaching the same to the other elements of the mechanism: l

Fig. 3 is a top view illustrating the compensating means, with a part thereof removed, and the means for maintaining said means in position relative to the remainder of the mechanism;

Fig. 4 is a sectional view taken on line 4 4 of Fig. 3;

Fig. 5 is a perspective view of the entire mechanism of the instrument, with the casing removed, illustrating another embodiment of the compensating means;

Fig. 6 is an enlarged sectional view illustrating the compensating means shown in Fig. 5`; and

`111g. :Imis an enlarged sectional view of another embodiment-.of the compensating means. illustrating the means for attaching the same to the other elements of the mechanism.

Referring to the drawings, and more particularly to Fig. 1, the invention is shown in the present instance as applied to a rate-ofeclimb indieating instrument mounted in a casing I0 and which, as shown,

including an opera g mechanism mounted on a frame of any suitable type and construction, comprises a rear frame member or plate II and a face plate I2, said plates being held in spaced relation in any suitable manner as by the spacers I3 and screws I4. Mounted in the frame thus constituted is a pressure responsive element ofany suitable type I5, that is adapted to operate any suitable indicator or pointer such as I6 when a pressure differential is established between the pressure inside the element and the pressure within the casing ing said element on the outside thereof.

pressure differential may be produced, for example, by providing communication between the in-` side of the pressure responsive element and the atmosphere outside the casing of the instrument, whilenterposing diffusing means between the outside atmosphere and the inside of the casing, as illustrated and described, for example, in the copending application of James E. Bevins, Serial No. 101,348, led September 17, 1936, now Patent 2,147,962, granted February 21, 1939.

As shown in the drawings, by way of example, the pressure responsive element I comprises a diaphragm capsule mounted in any suitable manner on a iiexible arm As illustrated in Figs. 1 to 4, inclusive, said novel means may comprise channel-shaped element I8 having a base I9 and upwardly extending sides I9a, said base being provided with slits 2li cut therein as illustrated 'in Fig. 3, whereby a resilient ytongue I9b is provided for flexibly supporting the channel in place. A block 2I extends across the tongue I9b ybetween said tongue and a bracket 22. Screws 23 passing through said tongue I9b and block 2I resiliently attach the channel to bracket 22. lBracket 22 is vprovided with upwardly extending arms 24, extending on both sides of said channel, andthese arms are attached to the rear frame member on plate II by means of screws 25. Arms 24 are sufficiently spaced from the sides of channel element I8 so that said element may move between said arms without contacting the same. Channel I8 is thereby held in position with respect to the other nelements of the mechanism with a portion of said channel extending through an opening 26 in rear plate II, the sides I9abeing provided with integral upwardly extending ears 21 adjacent the extremities of which is rotatably mounted the roller 21a on axle 28 held in place in said ears 21.

A sliding internally threaded block 29 which is held in slidable position by 'ears 21 is mounted on threaded bolt 3'I, whereby said block may be adjustably positioned upwardly and downwardly in order to provide a zero adjustment of the diaphragm as will be described in detail later.

On the opposite end of the channel I8 and carried by the ears 32 isa roller 33 rotatably mounted on axle 34 held in place in said ears 32. Roller 33 is cooperatively positioned with respect to the conical end 35a of threaded adjustment screw 35 which cooperates with screw threads 36 on the interior of an I-shaped element 31 fastened to the face plate I2 by means of lugs 38vand cooperating screw elements (not shown). Screw 35 may be rotated by inserting a tool such as a screw-driver in slot 39 thereof, whereby the cooperative position of the conicalend 35a with respect to roller 33 may be adjusted to, in turn. adjust the zero position ofthe instrument, this zero adjustment being utilized after the novel I1 comprising the novel' .means of the present invention.

and surround- This compensating means have been adjusted by means of elements 29 and 3|.

A second, channel-shaped element 40 is mounted in inverted position with respect-to channel element I8. The second channel element cornprises a base 4I with sides 42 integral therewith and extending downwardly therefrom, said sides being cut as shown at 43 whereby the second channel element may fulcrum. Downwardly extending wings 44, also integral with base 4I, are fastened to the upwardly extending sides I9a of channel element I8 by means of rivets or the like 45 as illustrated in Fig. 2. A block 46 is fastened to a tapped opening in base 4I by means of lscrew 41.

A thi'n metallic strip 48, which is readily responsive to changes in temperature, is attached at one end to the block 46 by brazing or in any other desired manner and extends over the top of 'block 46, screw 41 and roller 21a and is attached to the adjustable block 29 by means of rivets 49, as shown in Fig. 2. The tension on the thin strip 48 may, therefore, be adjusted by means of screw 3I and block 29 to, in turn, adjust the zero position of the diaphragm as will now be described in detail.

A hollow post 50 is fastened to the base 4I in any suitable manner as, for example, by peening the end of the post over against' said base 4I and thereby holding said post in place by means of shoulder 50a and peen-over portion 50h. A hollow internally threaded block 5I having a rounded extension l52 integral therewith is fastened to the post 50 by placing extension 52 within the hollow post 5.0, the block 5I being held in place within said post 59 bymeans of set screw 53 extending through the wall of the hollow post and cooperating with extension 52.

Pressure responsive diaphragm I5 is provided with a hollow central boss 54 (see Fig. 2) communicating .with the interior of said diaphragm.

`The central boss 54 is provided with a threaded portion 55 which is connected to the block 5I, the block 5I being first screwed to the threaded portion 55 and the extension 52 of said block 5I being then inserted into the post 50 whereby the diaphragm I5 is held in position connected to the novel compensating means I1 by means of set screw 53 as described above.

Upon adjustment of the tension of the thin strip 48 by means of screw 3I and block 29, the

. zero position of the diaphragm I5 may be thus initially adjusted while the compensating element I1 is being mounted in position and adjusted for the proper compensating effect.

After the compensating element I1Ahas been adjusted, a further adjustment ofthe diaphragm position may be obtained by means ofthe conically shaped threaded screw 35 cooperating with the roller 33 to adjust the position of the compensating element I1 in its entirety.

A tube 56 is connected to the central boss 54 of :the diaphragm whereby the interior of diaphra'gm I5 is placed in communication with the atmosphere outside the instrument in any suit- As shown in Fig. 1, said tube 56 that is suitably/ able manner. leads to a coupling member 51 vented to the outside atmosphere as hereinafter described.

In the manner shown and described in the above-mentioned copending application Serial No.. 101,348, suitable actuating connections and pressure differential means are provided for 'operatively assembling the mechanism of the in. strument, i f

be moved about slot 43 as a Referring to Fig. 1', suitable actuating connections are provided between said pressure responsive element I5 and the indicator or pointer |6.

collar 6| by a set screw 62 for rotation about a rock-shaft 69 journaled in a U-shaped bracket 64 which is fastened at'its base 64a in any desired manner to the rear plate II.` A block v65 is mounted for rotation with rock-shaft 63 and is provided with an arm 66 extending from one side thereof and an adjustable counterweight comprising wheel 61 mounted on screw 68 extending from the other side thereof. Arm 66, shown as partly behind rock-shaft arm60 in Fig. 1, is swung about the rock-shaft 63 in response to contraction and expansion of diaphragm, I 5.

Suitably mounted on face plate I2, as by means of spacers 69 and screws 10, is a plate 1| in which is suitably mounted a spindle 12. An arm or finger 13 extends from the spindle 12 and is engaged by the arm 66 for rotation thereby in one direction, and a siutable hairspring 14 tends to rotate the spindle 12 in the opposite direction whereby expansion and contraction of the pressure responsive element I6 is converted into rotation of the said spindle 12 in one direction or the other.

Acounterweighted gear sector 15 carried by spindle 'I2 meshes with a pinion 16 on a second spindle 11 that is rotatably mounted in a plate 18 held in spaced relation from the rst plate by suitable spacers 19 and screws 86. The spindle 'I1 extends through face plate I2 and carries at its outer end the pointer I6.

The above-described mechanism is mounted in the casing I which may be of any suitable material such as Bakelite, the face plate I2 being seated against shoulder 8| formed in said casing and being held therein by a `split ring 82 which expands into groove 83 also' formed in said casing. The casing is suitably closed as by means of a split spacing ring 84 and a cover glass 85 held in place by resilient ring 86 to thereby seal the casing at one end thereof.

The sole remaining opening in the'casing is sealed by means of coupling member 51 provided with ears 51a engaged by bolts 81 extending through casing I0, whereby a tight seal is provided between said coupling member and a bushin g 88, a suitable washer or gasket 89 being provided for this purpose if desired. Bushing 88 is internally threaded to receive a nipple 90 to which may be connected a suitable tube fitting, whereby the pressure responsive instrument may be vented to any desired point remote from the instrumentl itself.

Diffusion means of the type described in said above-mentioned copending application 101,349, for' example, provide means whereby equalization of the pressure inside and outside of diaphragm I- may be properly regulated. In the present embodiment, said means -comprise a hollow member 9| suitably connected to coupling member 51 by an airtight connection. Suitable diffusing elements are provided for closing the ends of said hollow member 9|. One of said elements, which is shown as a hollow porcelain tube 92 closed at one end and connected to the hollow member 9| at the other end, closes the right hand end of hollow member 9| and controls the diffusion of air between the inside of the instrument casing and the interior of said 'of a rock-shaft arm 60 adjustably mounted in a block |06 by means of the screw |06.

hollow member 9|, while a second similar porcelain member (not shown) is located within the hollow member l9| and controls the diffusion of air between the interior of said hollow member and the outside atmosphere by means of coupling member 51and nipple 9|). The hollow member 9| is also provided with an outlet in which is disposed a temperature controlled bypass valve, the stem 93 of which is controlled in.

its position by the temperature responsive element 94 adjustably positioned by screw 95. It is to4 be noted that temperature responsive element 94 is responsive to the amount of temperature change and is not actuated in response to the rate of said temperature change. The details of said diiiusing means do not constitute a part of the present invention and are fully illustrated and described in said above-mentioned application 101,348 to which reference is hereby made for the details of the construction thereof.

Referring to Fig. 5, another embodiment of the novel means of the present invention is illustrated in conjunction with the entire mechanism. The details of this embodiment are shown more clearly in Fig. 6.

The bottom channel I8 and the top channel 40 of the embodiment shown in Figs. 1 to 4, inelusive, are combined in the embodiment illustrated in Figs. 5 and 6 into one element comprising base 96 the sides 91 of which include a portion 91a extending upwardly to connect ,integrally with the base 98 of the upper channel-shaped member. The sides 99 of the upper channel member are turned upwardly in this embodiment, so that the pivoting point is located at |00, the point of reversal of the upwardly and the downwardly extending sides of the upper channel member. A triangular-shaped block IOI is brazed to the base 98 and the thin strip 48 is adjustably 'connected thereto by means of washer |02 and screw |03 and is adjustably connected to block 29 by screws |03a and strip |0312. The remainder of this embodiment of the novel compensating means is generically the same as illustrated in Figs. 1 to 4, inclusive. x

In Fig, 7 is illustrated a further embodiment of the novel rate of temperature change coml In this embodiment, the upper channel 40 of Figs. l to 4, inclusive, is eliminated entirely in order to simplify the construction of the compensating means the bottom channel being constructed as shown at I8a. Thin strip 48 is illustrated as passing over an intermediate roller |04 before being attached to the Expansion and contraction of the, thin strip 48 causes movement of the block about the shaft |01 upon which block |05 is mounted. Block |05 and spring |08 are joined by link |09. Upon movement of the block due to expansion or contraction of strip 48 diaphragm I 5 is moved accordingly.

The operation of the device is as follows: When .the pressure inside and voutside the element I5,

or in other words, the pressure inside of element I5 and inside of casing In are equal, pointer I6 may be adjusted to read zero on a suitable scale by means of the adjusting screw 35 in Figl/ l, which shifts the position of element I5 as described in detail above, f

Now, if there is an increase in altitude, the atmospheric pressure surrounding the instrument decreases in proportion to the rate of change in altitude or the rate of climb and the pressure within diaphragm I5 decreases.correspondingly since this element is in open communication with the atmospheric pressure. The pressure within the casing I0, however, cannot instantly equalize with the outside atmospheric pressure as the .gases within the casing must escape by means of the diffusing means including porcelain tube 92. The

pressure within casing I0, therefore, remains greater than the pressure of the atmosphere and hence greater than the pressure within diaphragm I5 so that diaphragm i5 is compressed to thereg by actuate the pointer I6 to indicate the rate of climb. If the increase in altitude is stopped and the instrument remains at a constant altitude, then the gases in casing I0 will escape through the diiusing means until the pressures within the casing and within diaphragm I5 are equal.

Whenever a pressure diierential is caused between the pressure inside of the casing In and the pressure of diaphragm I5, a certain period of time must elapse before the pressure can be equalized even though the atmospheric pressure remains constant. It is due to this fact that the novel means of the present invention are utilized.

If we assume, for example, that an instrument of the character described is mounted on an aircraft which is located in a heated hangar and that the craft is suddenly wheeled out of said hangar into a cold atmosphere, the sudden change of temperature will cause a reduction of the pressure inside of the casing because the volume of said casing remains `substantially constant. While the pressure inside of the diaphragm is likewise momentarily reduced,` the interior of the diaphragm being directly connected to the atmosphere, there quickly ensues a flow of air to said interior thereby maintaining'the pressure therein at the full atmospheric pressure.

The reduction in pressure within the casing, however, cannot be instantly equalizedby ordinary means since the diiusing means will permitonly a' regulated now of air therethrough. y

This sudden reduction ,in pressure within the casing, while the pressure is maintained at full atmospheric pressure within the diaphragm, causes diaphragm I5 to expand to thereby erroneously indicate a rate of climb, which in this case would be indicative of descent instead of climb as the vpressure inside of casing I0 is reduced. On instruments as previously provided, this error willv not be compensated for with Asufiicient dispatch, particularly when the craft must immediately take flight.

Upon such a'reduction in the air pressure within the casing, which reduction is due to a reduction in temperature, the thin strip d8, which is actuated by the rate bf temperature change, is

contracted in proportion to said rate of change of temperature since its thinness is such that it responds at greater speed to the temperature change than the remainder of the device to which .the thin strip is attached. Upon contraction of strip 48, the upper channel element -40 is pivoted about the slit 43 to thereby lift the upper channel element 4I), its base 4I, hollow post 50, block 5I and central boss 54 of the diaphragm I5 to thereby bodily raise the diaphragm to compensate for the expansion of the diaphragm that took place upon the reduction or pressure within casing Il), which reduction in pressure accompanied the sudden reduction in temperature.

As thin strip 48 is actuated only by rate of I change in temperature, it will be noted that as the diierent parts of the instrument assume the same temperature, the relative contraction of the strip is reduced until eliminated entirely. At the same time, however, the reduction of pressure.'

tains the volume of air, said means may also bel utilized with 'the separate expansion chamber type of -instrument since. by a studyI of the relationship between the temperature changes in the expansion chamber and the temperature changes in the casing, the novel compensating means can be so adjusted as to compensate the instrument for rate o'f change of temperature within the expansion chamber.

Although several embodiments of the invention have been illustrated and described, other changes and modifications in form, materials and relative arrangement of parts, which will now appear to those `skilled in the art, may be made without departing from the scope of the invention.

Reference, therefore, is to be had to the appendend claims for a definition of the limits of the invention.

What is claimed is:

1. In a device of the character described, means responsive to a pressure diierential, and means responsive to change of temperature affecting said device and effective only upon a rapid rate of change of temperature for bodily shifting said diierential pressure responsive means to compensate,4 errors which would otherwise be produced by changes in said temperature.

2. In an instrument of the class described, a substantially airtight casing, a pressure responsive element within said casing in communication with the atmosphere outside of said casing, retarding means whereby said casing is in communication with the atmosphere outside thereof, g

and temperature responsive means in said casing `effective only upon a rapid rate of change of `temperature for modifying the operation of said pressure responsive element.

3. In an instrument of the character described, a diaphragm, means leading from one side of said diaphragm to a source of varying pressure, flow retarding means leading from the other side of said -diaphragm to said source. and means responsive to change of temperature affecting said instrument, and effective only upon a rapid rate of change of temperature, said means comprising a thin metal strip and means connecting said diaphragm and said strip whereby upon extension and contraction thereof said diaphragm is displaced.

4. An linstrument of the character described, comprising a pressure responsive element and means mounting said element in position comprising a channel-shaped element resiliently xed in position, means for flexing said channel-shaped element, a second channel-shaped element connected to said rst channel element, means providing a pivot point about which said second channel may be adjusted, a thin metal strip attached to said second channel element at one end of said strip, means adjustably xing the other end of said strip whereby the tension thereon 75 may be adjusted, and means connecting said second channel to said pressure responsive element whereby upon expansion and contraction of said strip the position of said pressure responsive element is adjusted. y

5. In a device of the character described, a

pressure responsive element, indicating means. connected to said element for positioning thereby and means responsive to rate of temperature change for modifying the indication of said indicating means comprising a iii-st channel, means resiliently iixing said channel in position, a second channel integral with said first channel and opposite thereto,vmeans providing a pivot point in said'second channel about w h said second channel may be rocked, a thin strip attached at one end to said second channel whereby said second channel may be rocked about said pivot point upon expansion and contraction of said thin strip, and means connecting said-second channel to said pressure responsive element for moving the latter axially upon expansion and contraction of said strip.

6. In a device of the character described, a pressure responsive element, indicating,l means connected to said pressure responsive element for indicating the value of the pressure differential actuating said element, and means responsive to rate of change of temperature for modifying the indication of said indicating means, comprising a channel, means resiliently mounting said channel in position, a thin strip attached at one end thereof to said channel means for adjusting the tension of said strip, said strip rocking said channel about its resilient mounting upon the expansion and contraction of said strip, and means connecting said channel to said pressure responsive .element for bodily moving the latter along its operating axis upon rocking movement of said channel.

'7. A temperature rate of change compensating element comprising a channel, slits in the bottom of said channel providing a resilient mounting therefor, a second channel mounted opposite to said first channel and connected thereto, a slit in the sides of said second channel, and a thin strip of thermally expansible material connecting said ilrst and second channels wherebysaid second channel is rocked about said slits therein upon expansion and contraction of said thin strip.

8. In combination, an expansible diaphragm having a yielding wall subject to atmospheric pressure on one side thereof, means for retarding v the rate at which pressure on the other side of said yielding wall tends to become equal to a changing atmospheric Ipressure due to changes in altitude, means actuated by said yielding wall in accordance with the rate of change in altitude, and means responsive to change oi temperature affecting said diaphragm and eiective only upon a rapid rate of change of temperature for modifying the action of said actuated means.

9. In an instrument responsive to variations in pressure of the atmospheric air the combination with a chamber enclosing a volume of air; a pressure responsive member acted upon by the pressure of said volume of air; and indicating means connected to be actuated by said pressure responsive member; of an element responsive to a change in temperature ail'ecting at least a part of said instrument and eil'ective onlyupon a rapid rate of change of temperature, said element being connected to vary the operative relation between said pressure responsive member and said indicating means.

10. In a vertical speed'indicator the combination with a chamber enclosing a volume of air: a diierential pressure responsive member con# nected to respond to a diilerence in pressure between said chamber and the atmospheric air; a constricted passage connecting said chamber with the atmosphere; and indicating means connected to be actuated by said pressure responsive member; of an element responsive to a change in tem- .perature aiectingat least a part of said instrument and effective only upon a rapid rate of change of temperature, said element being oonnected to vary the operative relation between said pressure responsive member and said indicating means.

11. A vertical speed indicator comprising, in combination, a chamber enclosing a volume of air; a differential pressure responsive member connected to respond 'to a diierence in pressure between said chamber and the atmospheric air;

a constricted passage connecting said chamber with the atmosphere: indicating means connected to be actuated by said pressure responsive member, and means including two temperature responsive elements, one of said elements being arranged to assume, upon a change in temperature affecting said instrument, the temperature of the other element with a predetermined lag in time, said temperature responsive elements being arranged to increase and decrease the reading of the indicating means in response to a diiference in temperature between said elements.

I2. In an indicating instrument the combination of indicating means; a first temperature responsive element; a second temperature responsive element arranged to assume, upon a change in temperature, the temperature of said ilrst ele ment with a predetermined lag in time, said elements being connected to actuate said indicating means in response to a diierence in temperature of said elements. y

, ALFRED E. SIDWELL. 

